1. Field of the Invention
The present invention is directed to vehicle suspension system for use in automobiles, trucks and other vehicles.
2. Description of the Related Art
In the applicant""s earlier Australian patent application No. 19420/95, there is shown a vehicle suspension system including two laterally spaced front wheel assemblies and two laterally spaced rear wheel assemblies. In each of the arrangements described in the above noted patent application, a first coupling means for interconnecting laterally spaced wheel assemblies is respectively provided at the front and the rear ends of the vehicle. Second coupling means for respectively interconnecting the longitudinally adjacent wheel assemblies are provided on each side of the vehicle. The first coupling means primarily support the weight of the vehicle body and provide four wheel bounce resilience whereas the second coupling means provides roll attitude control for the vehicle. In the arrangements described in this patent application, the first coupling means are generally provided by a pair of contra-rotational torsion bars respectively located at the front and rear of the vehicle. The second coupling means are also provided by a pair of contra-rotational torsion bars respectively provided on each side of the vehicle. A lateral roll control arrangement links the second coupling means. This suspension system provides for movement of one wheel in one direction resulting in the longitudinally adjacent and laterally adjacent wheels being respectively urged in the opposite direction. Furthermore movement of both wheels on one side of the vehicle in one direction during roll movement of the vehicle will urge movement of both the wheels on the other side of the vehicle in the same direction to thereby control vehicle roll; Details of the vehicle suspension system described in the above noted patent application are incorporated herein by reference.
It has been found in practice that it is difficult to accommodate a vehicle suspension system of the above noted type into existing vehicles because of the limited space provided under these vehicles and the configuration of the components of the vehicle as they have not been specifically designed to allow for such a vehicle suspension system. More particularly, these above noted types of suspension system may input suspension loads into the body structure at different points to conventional suspension systems. Due to the mechanical advantage (or motion ratio) of some elements of the suspension linkages to the wheel, these suspension loads may cause deflection and therefore noise if input directly into the lightweight structures of modern monocoque (or unitary) construction vehicle body shells.
Additionally, in the suspension system described in the aforementioned Australian application, only one form of low roll stiffness bounce support means is disclosed. It may be advantageous to use alternative arrangements of low roll stiffness bounce support, to facilitate packaging of the suspension system on a wider range of vehicles. Alternatively, it may be advantageous for the roll control arrangement be used in conjunction with conventional independent support arrangements for each wheel, which may provide a roll stiffness and therefore a warp (or cross-axle articulation) stiffness.
The object of the present invention is therefore to provide a vehicle suspension system of the above noted type that can be accommodated under existing vehicles, preferably without inputting large loads into the body structure of the vehicle.
With this in mind, according to one aspect of the present invention provides a suspension system for a vehicle, the suspension system including:
two laterally spaced front wheel assemblies and two laterally spaced rear wheel assemblies, each wheel assembly including a wheel and a wheel mounting supporting the wheel to permit movement of the wheel in a generally vertical direction relative to a body of the vehicle;
bounce support means for supporting the vehicle body above the wheels and roll control means for controlling a roll attitude of the vehicle body with respect to the wheels;
said roll control means including respective second coupling means interconnecting each wheel assembly to the longitudinally adjacent wheel assembly, and further including transfer means interconnecting the second coupling means of each said pair of longitudinally adjacent wheel assemblies;
said second coupling means being adapted to urge in response to a movement of the wheel of one said wheel assembly in a substantially vertical direction a movement of the wheel of another said wheel assembly connected to said same second coupling means in an opposing direction relative thereto;
said second coupling means also including average movement generating means arranged to generate a movement therein substantially proportional to the average movement of the two wheels connected thereto on one side of the vehicle, said generated average including a factor for the roll moment distribution of the roll control means, the transfer means transferring said generated average movement of said second coupling means to the other said second coupling means on the opposite side of the vehicle;
wherein the loads generated in the average movement generation means and the transfer means are resolved in a localised structural area of the suspension system, and
wherein the bounce support means and roll control means respectively provide separate bounce and roll stiffness for the vehicle.
The suspension system can take advantage of spaces located under the vehicle to locate components which resolve the transverse suspension loads (generated in the roll control means) by suitable location of the structural area(s).
The second coupling means may be used on a vehicle provided with conventional independent supports (which provide additional roll stiffness).
However it may be preferable to provide bounce support means including respective first coupling means interconnecting each said wheel assembly to the laterally adjacent wheel assembly to provide a complete suspension system with substantially zero warp (or cross-axle articulation) stiffness.
Alternatively a compromise between conventional independent supports and the preferred interconnected supports may be chosen. The bounce support means for at least one pair of laterally spaced wheel assemblies may include at least a first coupling means interconnecting each said wheel assembly, said first coupling means supporting at least a portion of the load on the associated wheel assemblies whilst providing substantially no roll stiffness.
Where at least one first coupling means is provided, a height adjustment means may also be included to vary the average height of the body with respect to the associated wheels.
The substantially transverse suspension loads generated by the suspension arrangement may be resolved in at least one subframe upon which the vehicle body is supported. The front and rear wheel mountings may be respectively located on separate subframes, the roll control loads being resolved on at least one of the subframes. Alternatively, the roll control loads may be resolved on a further subframe. It is also envisaged that the transverse suspension loads be resolved in at least one reinforced structural area of the vehicle body.
The use of suspension subframes is advantageous for assembly of the vehicle on a production line. Parts or all of the suspension system may be produced as one or more sub-assemblies which are easily attached onto the vehicle body during whole vehicle assembly on a production line. One subframe could be provided with the suspension system attached to allow easy assembly and resolve all the loads.
Each second coupling means may include a roll lever arm for each said wheel assembly, the load in each roll lever arm varying in response to the warp and roll displacements of the wheels with respect to the body, and each second coupling means may include a linkage arrangement interconnecting the roll lever arms, the linkage arrangement of adjacent second coupling means being interconnected by the transfer means, the position of the connection of the transfer means to the linkage arrangements determining the roll moment distribution of the roll control means.
Each second coupling means may include at least one elongate torsion member connected to a said wheel mounting, the associated said roll lever arm extending from each torsion member.
The second coupling means may include a pair of elongate torsion members, one end of each torsion member being connected to and extending from a said wheel mounting, the other end of each torsion member including a roll lever arm extending from the torsion member, the roll lever arms being interconnected to by a linkage arrangement, the linkage arrangement of adjacent second coupling means being interconnected by the transfer means.
It is however also envisaged that the torsion members on both sides of the vehicle be aligned in an xe2x80x9cXxe2x80x9d configuration, with the transfer means located at a central location between the four wheel assemblies. In this configuration, the major rotational axes of the components of the first and second coupling means (ie the torsion members) are generally aligned towards a said structural area where loads from the first and second coupling means are resolved.
There are different methods which may be used to achieve the desired results from the transfer means. For example, the transfer means may include a Watts link.
Alternatively, if the roll lever arms of one said second coupling means are arranged to point substantially upwards and the roll lever arms of the other second coupling means on the opposite side of the vehicle point substantially downwards, then the transfer means interconnecting the linkage means may be a member which is substantially aligned with a transverse axis across the vehicle. This arrangement is a lever analogy of the gear arrangement shown in FIG. 3 of the Applicant""s above-mentioned Australian patent application No. 19420/95, which could also be used.
The linkage arrangement may include a flexible connection means at each end thereof for providing the respective connection to each roll lever arm.
According to a first possible arrangement, the first coupling means of at least one pair of laterally adjacent wheel assemblies may include a bounce lever arm for each wheel assembly, the load in each bounce lever arm varying in response to the bounce displacements and loads on the associated wheel assemblies. The first coupling means may further include a connection means interconnecting the bounce lever arm of one wheel assembly with the bounce lever arm of the laterally adjacent wheel assembly.
At least one of the first coupling means may include at least one torsion bar interconnected between at least one wheel mounting and the associated bounce lever arm.
The torsion members of at least one second coupling means may be hollow, a said torsion bar of the first coupling means being located within each said torsion member, with one end of the torsion bar being fixedly connected to the torsion member.
The bounce lever arm may extend from the end of the torsion bar opposite to the fixed end thereof. Alternatively, an aperture may be provided through the wall of the torsion member to provide clearance for the bounce lever arm to extend from the torsion bar. This provides a relatively compact arrangement which can more readily be positioned into a vehicle.
At least one of the torsion members of the second coupling means may include a bar extension from the torsion member, the bar extension forming part of the first coupling means. The bar extension may be integral with or fixedly secured to the torsion member. The bar extension may include a bounce lever arm extending therefrom. The first coupling means may also include a resilient means coupled at each end thereof to the bounce lever arms of laterally spaced bar extensions of the torsion members.
The connection means of the bounce supports may be a relatively rigid member interconnecting the bounce lever arms of laterally adjacent torsion bars.
Alternatively, the connection means interconnecting the bounce lever arms of laterally adjacent torsion bars may include a resilient means.
The resilient means may include a spring member and/or an hydraulic ram in fluid communication with an accumulator.
According to a second aspect of the invention, the first coupling means of at least one pair of said laterally adjacent wheel assemblies may include a pair of fluid rams, the fluid rams being respectively connected to the wheel mounts of laterally adjacent wheel assemblies, the hydraulic rams being connected by a fluid conduit to provide fluid communication therebetween, and an accumulator located on the fluid conduit.
According to yet another aspect of the present invention, there is provided an elongate suspension member for a vehicle suspension system including a tubular member, and a torsion bar accommodated within the tubular member, one end of the tubular member being fixedly secured to a wheel assembly, the other end being connected to one end of the torsion bar. A lever arm may extend from the other end of the torsion bar, the lever arm being connected to the lever arm associated with the laterally adjacent wheel assembly.
According to yet another alternative, one end of the vehicle may include different types of the first coupling means described above at different ends of the vehicle.
According to another aspect of the invention, there is provided a vehicle incorporating a suspension system including any aspects of the above described invention.
It will be convenient to further describe the invention by reference to the accompanying drawings which illustrate preferred embodiments of the invention. Other embodiments of the invention are possible, and consequently the particularity of the accompanying drawings is not to be understood as superseding the generality of the proceeding description of the invention.